Abstract: Forests play a key role in regulating greenhouse gas fluxes. With the increasing of plantation area, much attention has been paid to greenhouse gas flux and its response to fertilization. In order to identify the effects of nitrogen fertilization on the greenhouse gas fluxes of soilatmosphere interface in growing and nongrowing seasons in Eucalyptus plantations, low, middle and high nitrogen fertilization treatments (84.2, 166.8 and 333.7 kg N·hm^-2) and no fertilization (control) were established in Eucalyptus plantations in Guangxi, southern China. Greenhouse gas fluxes of soilatmosphere interface were measured by using the static chambergas chromatograph method. The results showed that the annual mean fluxes of CO₂, CH₄ and N₂O were 214-271 mg CO₂·m^-2·h^-1, -47--37 kg CH₄·m^-2·h^-1 and 16-203 kg N₂O·m^-2·h^-1 in Eucalyptus plantations, respectively. The fluxes of soil CO₂ emission were higher in growing season than in nongrowing season, but no significant seasonal variations were observed for the fluxes of CH₄ and N₂O. Nitrogen fertilization significantly increased the annual mean fluxes of soil CO₂ and N₂O emission, especially in the growing season (April to September). The annual mean fluxes of soil CH₄ uptake showed a decreased trend with nitrogen fertilization, which suggested soil CH₄ uptake was inhibited by nitrogen fertilization. Our results suggested that reasonable nitrogen fertilization according to the seasonal variation of greenhouse gas emission should not be neglected for decreasing soil greenhouse gas emission in Eucalyptus plantations.

Key words: winter wheat, planting green manure, yield, dryland, straw retention, plastic film mulching, nutrient concentration.